Microgrid and control method, device thereof

Abstract

The application discloses a microgrid and a control method and device thereof. The microgrid control method comprises the following steps: acquiring real-time power of a main transformer node, judging the power of the main transformer node according to a change trend of the real-time power in a preset time period, and determining maximum output power of an energy storage system; and determining output power of the energy storage system at a current time according to the power judgment result of the main transformer node and the maximum output power of the energy storage system, in combination with output power of the energy storage system at a previous time. Compared with the prior art, the embodiment of the application can actively control the power of the main transformer, and relieve the problem of frequent overload faults of the main transformer.

Description

Technical Field

[0001] This invention relates to the field of power generation technology, and in particular to a microgrid and its control method and apparatus. Background Technology

[0002] With the gradual depletion of conventional energy sources and increasingly severe environmental pollution, new energy sources and distributed generation technologies have received widespread attention and development in recent years. Distributed generation generally refers to small-scale, modular, decentralized power generation systems connected to the distribution system and located near users to supply power to them. Connecting distributed generation energy supply systems to the main power grid in the form of microgrids (microgrids) and allowing them to support each other is the most effective way to maximize the efficiency of distributed generation energy supply systems.

[0003] In existing technologies, microgrid user-side renewable energy power plants typically include photovoltaic (PV) systems, energy storage systems, wind power systems, and electrical loads. The output of PV and wind power systems fluctuates, and the electrical load also fluctuates depending on the season and operational conditions. However, the capacity of the main transformer within the power plant is fixed, and overload is not permitted; otherwise, the power plant cannot operate normally. Current control methods typically initiate overload control actions only after a main transformer overload occurs. This control method is relatively passive; even if the overload is suppressed, repeated overloads can still occur, leading to large power fluctuations and frequent overload faults within the power plant. Summary of the Invention

[0004] This invention provides a microgrid and its control method and device to actively control the power of the main transformer and alleviate the problem of frequent overload faults of the main transformer.

[0005] According to one aspect of the present invention, a microgrid control method is provided, comprising:

[0006] The real-time power of the main transformer node is obtained, and the power of the main transformer node is predicted based on the trend of the real-time power change within a preset time period, and the maximum output power of the energy storage system is determined.

[0007] Based on the power prediction result of the main transformer node and the maximum output power of the energy storage system, combined with the output power of the energy storage system at the previous moment, the output power of the energy storage system at the current moment is determined.

[0008] Optionally, the step of predicting the power of the main transformer node based on the real-time power change trend within a preset time period includes:

[0009] Calculate the overload boundary threshold based on the specifications of the main transformer;

[0010] Based on the overload boundary threshold and the real-time power within the preset time period, calculate the overload difference sample of the main transformer within the preset time period to form an overload difference sample set;

[0011] Based on the trend of the values ​​in the overload difference sample set, a first power limit is calculated; wherein, the first power limit is the maximum output power of the main transformer node.

[0012] Optionally, the method for calculating the first power limit includes:

[0013] If the trend of the values ​​in the overload difference sample set is monotonically increasing, then the value with the largest value in the overload difference sample set is selected as the first power limit.

[0014] If the trend of the overload difference sample set is monotonically decreasing or non-monotonic, then the values ​​in the overload difference sample set are filtered and normalized to obtain the first power limit.

[0015] Optionally, the filtering and normalization processing of the values ​​in the overload difference sample set includes:

[0016] Filter out the outlier values ​​in the overload difference sample set, and calculate the average value of the remaining values;

[0017] The first power limit is calculated based on the average value and the normalization coefficient.

[0018] Optionally, the method for calculating the overload difference sample of the main transformer within the preset time period further includes:

[0019] The overload difference sample is calculated by combining the empirical value of the overload dead zone.

[0020] Optionally, after calculating the first power limit, the method further includes:

[0021] Based on the conversion relationship between the main transformer and the energy storage system, the first power limit is converted to obtain the second power limit; wherein, the second power limit is the maximum output power of the energy storage system.

[0022] Optionally, the method for determining the current output power of the energy storage system includes:

[0023] Based on the power prediction result of the main transformer node, determine whether the main transformer is over-limit; if so, the energy storage system performs output power adjustment under over-limit conditions; otherwise, the energy storage system performs output power adjustment under non-over-limit conditions.

[0024] The method for adjusting the output power of the energy storage system includes: determining an adjustment step size based on the maximum output power of the energy storage system; and gradually adjusting the output power according to the adjustment step size and the output power of the energy storage system at the previous moment.

[0025] Optionally, the method for regulating the output power of the energy storage system further includes:

[0026] The initial value of the adjustment amount of the energy storage system is calculated based on the overload difference sample set.

[0027] Optionally, the method for calculating the initial value of the adjustment amount includes:

[0028] The maximum and minimum values ​​in the overload difference sample set are selected;

[0029] The initial value of the adjustment amount is obtained by dividing the maximum value by the minimum value.

[0030] Optionally, the method for determining the adjustment step size includes:

[0031] The adjustment step size is obtained by dividing the interval between the initial value of the adjustment amount and the maximum value of the adjustment amount into equal parts.

[0032] According to another aspect of the present invention, a microgrid control device is provided, comprising:

[0033] The power prediction module is used to obtain the real-time power of the main transformer node, predict the power of the main transformer node based on the trend of the real-time power change within a preset time period, and determine the maximum output power of the energy storage system.

[0034] The power adjustment module is used to determine the current output power of the energy storage system based on the power prediction result of the main transformer node and the maximum output power of the energy storage system, combined with the output power of the energy storage system at the previous moment.

[0035] According to another aspect of the present invention, a microgrid is provided, comprising: a main transformer and an energy storage system, wherein the main transformer is used to convert the energy storage system and other systems in the microgrid, and the energy storage system performs the microgrid control method as described in any embodiment of the present invention.

[0036] This invention, through its embodiments, predicts the power of the main transformer node based on the real-time power change trend within a preset time period and determines the maximum output power of the energy storage system. It also determines the current output power of the energy storage system by combining the output power of the energy storage system at the previous moment. This achieves over-limit prediction of the main transformer, actively controlling it to prevent overload, thus contributing to the stable and reliable operation of the microgrid without overload faults. Specifically, predicting the power of the main transformer node and determining the maximum output power of the energy storage system allows for advance prediction of the main transformer's power limit at the next moment, providing a power reference for the energy storage system's output. This method can be called a power feedforward method. Combining the energy storage system's output power at the previous moment with the current moment's output power allows for control of the energy storage system's output power to follow the power limit according to a set adjustment amount, ensuring maximum output power in the absence of overload. This method can be called an energy storage power following control method. Therefore, this invention, through power feedforward and energy storage power following, achieves active control of the main transformer's power, alleviating the problem of frequent main transformer overload faults.

[0037] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A schematic diagram of a microgrid topology provided in an embodiment of the present invention;

[0040] Figure 2 A flowchart illustrating a microgrid control method provided in an embodiment of the present invention;

[0041] Figure 3 A schematic diagram illustrating a process for predicting the power of a main transformer node and determining the maximum output power of an energy storage system, provided as an embodiment of the present invention;

[0042] Figure 4 A schematic diagram of an energy storage power follower provided in an embodiment of the present invention;

[0043] Figure 5 A flowchart illustrating a method for determining the current output power of an energy storage system according to an embodiment of the present invention;

[0044] Figure 6 A flowchart illustrating another method for determining the current output power of an energy storage system according to an embodiment of the present invention;

[0045] Figure 7 This is a schematic diagram of a microgrid control device provided in an embodiment of the present invention. Detailed Implementation

[0046] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0047] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0048] This invention provides a microgrid control method for active overload control of a main transformer. The control method is executed by a microgrid control device, which can be implemented in software and / or hardware.

[0049] To clearly illustrate the microgrid control method provided in the embodiments of the present invention, the structure of the microgrid provided in the embodiments of the present invention will first be described. Figure 1 This is a schematic diagram of a microgrid topology provided in an embodiment of the present invention. See also... Figure 1 The microgrid includes a main transformer 10 and an energy storage system 20. The main transformer 10 is used to convert the power of the energy storage system 20 and other systems in the microgrid. The energy storage system 20 executes the microgrid control method provided in any embodiment of the present invention. The energy storage system 20 can act as a generator, transmitting electrical energy to the main transformer 10; it can also act as a load, absorbing electrical energy from the main transformer 10. Therefore, the energy storage system 20 can regulate the power of the main transformer 10.

[0050] See also Figure 1 Optionally, the microgrid also includes a metering device 30, which is used to meter the electrical quantities of the main transformer 10 nodes. For example, the metering device 30 measures and outputs the active power of the main transformer 10 nodes.

[0051] See also Figure 1 Optionally, the microgrid may also include other renewable energy systems, such as photovoltaic system 40 or wind power system 50. Both photovoltaic system 40 and wind power system 50 are power generation systems, serving as the source of electrical energy. The electrical energy generated by photovoltaic system 40 and wind power system 50 can also charge energy storage system 20 or be transmitted to the power grid via main transformer 10.

[0052] See also Figure 1 Optionally, the microgrid also includes an electrical load 60, such as equipment power consumption or site lighting. The electrical load 60 is the receiving end of electrical energy, and at least one of the main transformer 10, energy storage system 20, photovoltaic system 40, and wind power system 50 provides electrical energy to the electrical load 60. The main transformer 10, energy storage system 20, photovoltaic system 40, wind power system 50, and electrical load 60 are connected via a busbar 70.

[0053] Figure 2 This is a schematic flowchart illustrating a microgrid control method provided in an embodiment of the present invention. See also... Figure 2 The microgrid control method includes the following steps:

[0054] S110. Obtain the real-time power of the main transformer node, predict the power of the main transformer node based on the real-time power change trend within a preset time period, and determine the maximum output power of the energy storage system.

[0055] The real-time power of the main transformer node can be acquired, for example, through a metering device. The acquired real-time power is sorted chronologically and exhibits a certain regularity. By analyzing this regularity (e.g., using inferential statistical methods), the power of the transformer node at future moments can be predicted, thus achieving power prediction. The time span of the preset time period can be set as needed. Specifically, a longer preset time period requires more real-time power data but results in a more accurate prediction; a shorter preset time period results in lower accuracy but requires less real-time power data.

[0056] See Figure 1The microgrid includes an energy storage system 20. Unlike other systems in the microgrid, the energy storage system 20 not only provides electrical energy but also absorbs it. Specifically, when the output power of the energy storage system 20 is positive, it indicates that the energy storage system 20 is providing electrical energy; when the output power of the energy storage system 20 is negative, it indicates that the energy storage system 20 is absorbing electrical energy. Therefore, by adjusting the power of the energy storage system 20, the power of the main transformer 10 node can be adjusted to prevent the main transformer 10 from exceeding its limits.

[0057] S120. Based on the power prediction results of the main transformer node and the maximum output power of the energy storage system, combined with the output power of the energy storage system at the previous moment, determine the output power of the energy storage system at the current moment.

[0058] The power prediction result can characterize whether the main transformer has an over-limit risk, thus determining the control strategy. The maximum output power of the energy storage system can be matched with the power prediction result to ensure that the main transformer does not exceed the limit. Furthermore, this embodiment of the invention further limits the output power of the energy storage system, that is, by combining the output power of the energy storage system at the previous moment to determine the output power of the energy storage system at the current moment. This setting in S120 enables gradual adjustment of the energy storage system, ensuring the stability of the microgrid's operating state. The reason is, see [link to relevant documentation] Figure 1 The microgrid includes a main transformer 10, an energy storage system 20, electrical loads 60, and other new energy power generation systems. When the output power of the energy storage system 20 fluctuates significantly, it causes large voltage fluctuations on the bus 60, affecting the stability of the microgrid operation. Therefore, gradually adjusting the current output power of the energy storage system 20 based on the previous output power is beneficial to the stability of the microgrid's operation.

[0059] In summary, this invention, by predicting the power of the main transformer node based on the real-time power change trend within a preset time period and determining the maximum output power of the energy storage system, and by combining the output power of the energy storage system at the previous moment to determine the current output power of the energy storage system, achieves over-limit prediction of the main transformer and actively controls the main transformer to prevent overload, thereby facilitating the stable and reliable operation of the microgrid without overload faults. Specifically, predicting the power of the main transformer node and determining the maximum output power of the energy storage system allows for advance prediction of the power limit of the main transformer at the next moment, providing a power reference for the energy storage system's output; this method can be called a power feedforward method. Combining the output power of the energy storage system at the previous moment to determine the current output power of the energy storage system allows for control of the energy storage system's output power to follow the power limit according to a set adjustment amount, ensuring that the energy storage system outputs at its maximum capacity under overload conditions; this method can be called an energy storage power following control method. Therefore, this invention, through power feedforward and energy storage power following, achieves active control of the main transformer's power, alleviating the problem of frequent main transformer overload faults.

[0060] In the above embodiments, there are various specific implementation methods for power feedforward and energy storage power following. Several of them will be described below, but they are not intended to limit the present invention.

[0061] Figure 3 This is a schematic flowchart illustrating how to predict the power of a main transformer node and determine the maximum output power of an energy storage system, as provided in an embodiment of the present invention. (See also...) Figure 3 In one embodiment of the present invention, optionally, the power of the main transformer node is predicted based on the real-time power change trend within a preset time period, and the maximum output power of the energy storage system is determined. That is, the determination of power feedforward includes the following steps:

[0062] S210. Obtain the real-time power of the main transformer node and calculate its overload boundary threshold according to the specifications of the main transformer.

[0063] The real-time power includes active power P and reactive power Q. The active power within a preset time period constitutes an active power sample set, and the reactive power within the preset time period constitutes a reactive power sample set. Optionally, the real-time power is reactive power Q, and the specifications of the main transformer include: rated capacity P. e Optimize the derating factor δ, etc., in conjunction with reactive power Q and rated capacity P. e The overload threshold (or overload threshold power) of the main transformer can be calculated using the optimal derating factor δ. The calculation formula for the overload threshold can be, for example: One real-time power corresponds to one overload boundary threshold, and the overload boundary thresholds within a preset time period constitute the overload boundary threshold sample set.

[0064] S220. Based on the overload boundary threshold and the real-time power within a preset time period, calculate the overload difference sample of the main transformer within the preset time period to form an overload difference sample set.

[0065] Among them, the overload difference sample characterizes the overload degree of the main transformer. Compared with other parameters of the main transformer, the overload difference sample combines the active power P, reactive power Q and specifications of the main transformer (including rated capacity P). e And the preferred derating factor δ) can more accurately determine the overload condition of the transformer.

[0066] Optionally, the method for calculating the overload difference sample of the main transformer within a preset time period further includes: calculating the overload difference sample by combining empirical values ​​of the overload dead zone. For example, the formula for calculating the overload difference sample is: |ΔP|=|P th -abs(P)-σ|, where abs(P) is the absolute value of the active power P, σ is the dead zone empirical value, and the overload difference samples within the preset time period constitute the overload difference sample set. The addition of the dead zone empirical value σ helps to ensure that the power of the main transformer does not exceed the limit. Figure 4 This is a schematic diagram of an energy storage power follower provided in an embodiment of the present invention. See also... Figure 4 Because of the setting of the dead zone empirical value σ, there is a certain range between the energy storage output power and the actual energy storage power limit. In this way, when the real-time power change of the main transformer node causes the real-time power limit to change, the energy storage output power can be controlled to both follow the power limit and not exceed the power limit, thus completing the active overload protection function.

[0067] S230. Calculate the first power limit based on the trend of the values ​​in the overload difference sample set; wherein, the first power limit is the maximum output power of the main transformer node.

[0068] The first power limit is calculated using different methods depending on the changing trend of the values ​​in the overload difference sample set. Optionally, if the trend of the values ​​in the overload difference sample set is monotonically increasing, then the value with the largest value in the overload difference sample set is selected as the first power limit, i.e., the first power limit P. 限1 =max{|△P|}.

[0069] If the trend of the overload difference sample set is monotonically decreasing or non-monotonic, the values ​​in the overload difference sample set are filtered and normalized to obtain a first power limit. Optionally, the filtering and normalization process for the values ​​in the overload difference sample set includes: filtering out outliers from the overload difference sample set, calculating the average value of the remaining values, and calculating the first power limit based on the average value and a normalization coefficient. For example, the formula for calculating the first power limit is: Where λ is a normalization coefficient greater than 1, and n is the total number of overload difference samples ΔP within the preset time T.

[0070] S240. Based on the conversion relationship between the main transformer and the energy storage system, the first power limit is converted to obtain the second power limit; wherein, the second power limit P 限2 This represents the maximum output power of the energy storage system.

[0071] There is a certain conversion relationship between the maximum output power of the main transformer and the maximum output power of the energy storage system. This conversion relationship is common knowledge in this field and will not be elaborated here.

[0072] Through steps S210-S240, the power of the main transformer node is predicted, and the maximum output power of the energy storage system is determined, thus realizing the determination of the power feedforward. This embodiment of the invention is configured in such a way that the prediction results are accurate and easy to implement.

[0073] Figure 5 This is a flowchart illustrating a method for determining the current output power of an energy storage system according to an embodiment of the present invention. (See also...) Figure 5 In one embodiment of the present invention, optionally, the method for determining the current output power of the energy storage system, i.e., the energy storage power following method, includes the following steps:

[0074] S310. Determine whether the main transformer exceeds the limit based on the power prediction result of the main transformer node; if so, execute S320; otherwise, execute S330.

[0075] Optionally, comparing the active power of the main transformer with the first power limit can determine whether the main transformer exceeds the limit. For example, if the active power of the main transformer is greater than the first power limit, it is predicted that the main transformer exceeds the limit; otherwise, it is predicted that the main transformer does not exceed the limit.

[0076] S320, Energy storage system performs output power regulation under over-limit conditions.

[0077] Regardless of whether the main transformer exceeds its limits, the output power of the energy storage system must be adjusted gradually to maintain the stability of the microgrid. Optionally, the method for adjusting the output power of the energy storage system includes: determining the adjustment step size based on the maximum output power of the energy storage system (i.e., the second power limit); and gradually adjusting the output power based on the adjustment step size and the output power of the energy storage system at the previous moment.

[0078] S330, the energy storage system performs output power regulation under conditions where the limits are not exceeded.

[0079] Similar to over-limit time, the method for adjusting the output power of an energy storage system includes: determining the adjustment step size based on the maximum output power of the energy storage system; and gradually adjusting the output power based on the adjustment step size and the output power of the energy storage system at the previous moment.

[0080] As can be seen from S310-S330, the methods for adjusting the output power of the energy storage system are different when the main transformer is predicted to be over-limit and when it is not over-limit, in order to achieve the effectiveness and reliability of the adjustment.

[0081] Figure 6 This is a flowchart illustrating another method for determining the current output power of an energy storage system according to an embodiment of the present invention. This method is a further refinement of the foregoing embodiments; see below. Figure 6 In one embodiment of the present invention, optionally, the method for determining the current output power of the energy storage system, i.e., the energy storage power following method, includes the following steps:

[0082] S410, The output power of the energy storage system at the previous moment is configured to be the second power limit P. 限2 The adjustment amount at the previous moment was the initial value of the adjustment amount. That is, the output power at the previous moment = the second power limit P. 限2 The adjustment amount at the previous moment equals the initial value of the adjustment amount.

[0083] The initial value of the regulation amount of the energy storage system can be 0, or it can be calculated based on the overload difference sample set. Optionally, the maximum value ΔP in the overload difference sample set is selected. max and minimum value ΔP min ; the maximum value ΔP max Calculate the quotient ΔP with the minimum value min The initial value of the adjustment amount is obtained. For example, the formula for calculating the initial value of the adjustment amount is the adjustment amount.

[0084] S420. Based on the power prediction results of the main transformer node, determine whether the main transformer exceeds the limit, that is, determine whether the real-time active power P of the main transformer is greater than the first power limit P. 限1 If yes, then execute S470; otherwise, execute S430.

[0085] S430. Sum the adjustment amount from the previous time step with the adjustment step size to obtain the adjustment amount at the current time step; that is, the adjustment amount at the current time step = the adjustment amount from the previous time step step size + the adjustment step size.

[0086] If the main transformer is not over-limited, it means that the power of the main transformer can be further increased. In this case, increasing the adjustment amount at the current moment can increase the output power of the energy storage system and discharge the energy storage system without exceeding the limit of the main transformer, so as to ensure that there is enough capacity to absorb electrical energy when the energy storage system needs to be charged.

[0087] Optionally, the method for determining the adjustment step size includes: equally dividing the interval between the initial value and the maximum value of the adjustment amount to obtain the adjustment step size. For example, the adjustment step size can be evenly divided according to the initial value up to 100%, such as... Where m is an integer value greater than 1.

[0088] S440. Determine if the current adjustment amount is greater than 100%; if yes, execute S460; otherwise, execute S450.

[0089] Among them, the adjustment amount at the current moment should be ensured to be within 100% to ensure that the output power of the energy storage system is within the second power limit.

[0090] S450: Multiply the output power of the previous moment by the adjustment amount of the current moment to obtain the output power of the current moment.

[0091] S460: Set the current adjustment amount to 100%, i.e., the current adjustment amount = 100%. Then execute S450.

[0092] S470. Calculate the difference between the adjustment amount at the previous moment and the adjustment step size to obtain the adjustment amount at the current moment; that is, the adjustment amount at the current moment = the adjustment amount at the previous moment - the adjustment step size.

[0093] In the case of the main transformer exceeding its limits, it indicates a reduction in the transformer's power. Reducing the current adjustment amount is equivalent to reducing the output power of the energy storage system. Specifically, if the energy storage system's output power was positive in the previous moment, the output power is reduced, or even changed from positive to negative, to discharge the energy storage system. If the energy storage system's output power was negative in the previous moment, the discharge is further increased. This allows the system to absorb active power from the bus when the main transformer is about to exceed its limits.

[0094] S480. Determine whether the adjustment amount at the current moment is less than or equal to 0; if yes, execute S450; otherwise, return to execute S420.

[0095] The S410-S480 series control method for energy storage power tracking is implemented. This control method has good stability for over-limit control of the main transformer and is easy to implement.

[0096] In summary, the embodiments of the present invention achieve active control of the main transformer's power through power feedforward and energy storage power following, thereby alleviating the problem of frequent overload faults in the main transformer.

[0097] This invention also provides a microgrid control device, which can be implemented by software and / or hardware. This device can execute the microgrid control device provided in any embodiment of this invention, and its technical principle and the resulting effect are similar.

[0098] Figure 7 This is a schematic diagram of a microgrid control device provided in an embodiment of the present invention. See also... Figure 7 The microgrid control device includes:

[0099] The power prediction module 100 is used to obtain the real-time power of the main transformer node, predict the power of the main transformer node based on the real-time power change trend within a preset time period, and determine the maximum output power of the energy storage system.

[0100] The power adjustment module 200 is used to determine the current output power of the energy storage system based on the power prediction results of the main transformer node and the maximum output power of the energy storage system, combined with the output power of the energy storage system at the previous moment.

[0101] Optionally, the power prediction module includes:

[0102] The overload boundary threshold calculation unit is used to calculate the overload boundary threshold according to the specifications of the main transformer.

[0103] The overload difference sample set composition unit is used to calculate the overload difference sample of the main transformer within the preset time period based on the overload boundary threshold and the real-time power within the preset time period, and to form the overload difference sample set.

[0104] The first power limit calculation unit is used to calculate the first power limit based on the trend of the values ​​in the overload difference sample set; wherein, the first power limit is the maximum output power of the main transformer node.

[0105] Optionally, the first power limit calculation unit is also used for:

[0106] If the trend of the values ​​in the overload difference sample set is monotonically increasing, then the value with the largest value in the overload difference sample set is selected as the first power limit.

[0107] If the trend of the overload difference sample set is monotonically decreasing or non-monotonic, then the values ​​in the overload difference sample set are filtered and normalized to obtain the first power limit.

[0108] Optionally, the first power limit calculation unit is further configured to, when performing filtering and normalization processing on the values ​​in the overload difference sample set, include:

[0109] Filter out outliers from the overload difference sample set and calculate the average of the remaining values.

[0110] The first power limit is calculated based on the average value and the normalization coefficient.

[0111] Optionally, the overload difference sample set constituting unit is further used to, when calculating the overload difference sample of the main transformer within a preset time period, also include:

[0112] Based on empirical values ​​of overload dead zone, calculate overload difference samples.

[0113] The power prediction module also includes a second power limit calculation unit, which is used to convert the first power limit according to the conversion relationship between the main transformer and the energy storage system to obtain the second power limit; wherein, the second power limit is the maximum output power of the energy storage system.

[0114] Optionally, the power adjustment module is also used to: determine whether the main transformer is over-limit based on the power prediction result of the main transformer node; if so, the energy storage system performs output power adjustment under over-limit conditions; otherwise, the energy storage system performs output power adjustment under non-over-limit conditions.

[0115] The method for regulating the output power of an energy storage system includes: determining the regulation step size based on the maximum output power of the energy storage system; and gradually regulating the output power based on the regulation step size and the output power of the energy storage system at the previous moment.

[0116] Optionally, the power adjustment module is also used for:

[0117] Based on the overload difference sample set, calculate the initial value of the regulation of the energy storage system.

[0118] Optionally, the power adjustment module is also used to calculate the initial value of the adjustment amount using the following methods:

[0119] Filter out the maximum and minimum values ​​in the overload difference sample set;

[0120] The initial value of the adjustment amount is obtained by dividing the maximum and minimum values.

[0121] Optionally, the power adjustment module is also used to determine the adjustment step size using the following methods:

[0122] Divide the interval between the initial value and the maximum value of the adjustment into equal parts to obtain the adjustment step size.

[0123] In summary, this embodiment of the invention, by setting up a power prediction module and a power adjustment module, achieves over-limit prediction of the main transformer, actively controlling the main transformer to prevent overload, which is beneficial for the stable and reliable operation of the microgrid without overload faults. Specifically, the power prediction module can predict the power of the main transformer nodes and determine the maximum output power of the energy storage system, realizing the advance prediction of the main transformer's power limit at the next moment, providing a power reference for the energy storage system's output. This method can be called a power feedforward method. The power adjustment module can combine the energy storage system's output power at the previous moment to determine the current moment's output power, realizing the control of the energy storage system's output power to follow the power limit according to the set adjustment amount, ensuring that the energy storage system outputs at its maximum capacity under overload conditions. This method can be called an energy storage power following control method. Therefore, this embodiment of the invention, through power feedforward and energy storage power following, achieves active control of the main transformer's power, alleviating the problem of frequent main transformer overload faults.

[0124] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0125] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A microgrid control method, characterized in that, include: The real-time power of the main transformer node is obtained, and the power of the main transformer node is predicted based on the trend of the real-time power change within a preset time period, and the maximum output power of the energy storage system is determined. Based on the power prediction result of the main transformer node and the maximum output power of the energy storage system, combined with the output power of the energy storage system at the previous moment, the current output power of the energy storage system is determined, and the output power of the energy storage system is controlled to follow the maximum output power according to the set adjustment amount. The step of predicting the power of the main transformer node based on the real-time power change trend within a preset time period includes: Calculate the overload boundary threshold based on the specifications of the main transformer; Based on the overload boundary threshold and the real-time power within the preset time period, calculate the overload difference sample of the main transformer within the preset time period to form an overload difference sample set; Based on the trend of the values ​​in the overload difference sample set, a first power limit is calculated; wherein, the first power limit is the maximum output power of the main transformer node.

2. The method according to claim 1, characterized in that, The calculation method for the first power limit includes: If the trend of the values ​​in the overload difference sample set is monotonically increasing, then the value with the largest value in the overload difference sample set is selected as the first power limit. If the trend of the overload difference sample set is monotonically decreasing or non-monotonic, then the values ​​in the overload difference sample set are filtered and normalized to obtain the first power limit.

3. The method according to claim 2, characterized in that, The filtering and normalization process for the values ​​in the overload difference sample set includes: Filter out the outlier values ​​in the overload difference sample set, and calculate the average value of the remaining values; The first power limit is calculated based on the average value and the normalization coefficient.

4. The method according to claim 1, characterized in that, The method for calculating the overload difference sample of the main transformer within the preset time period also includes: The overload difference sample is calculated by combining the empirical value of the overload dead zone.

5. The method according to claim 1, characterized in that, After calculating the first power limit, the method further includes: Based on the conversion relationship between the main transformer and the energy storage system, the first power limit is converted to obtain the second power limit; wherein, the second power limit is the maximum output power of the energy storage system.

6. The method according to claim 1, characterized in that, The method for determining the current output power of the energy storage system includes: Based on the power prediction result of the main transformer node, determine whether the main transformer is over-limit; if so, the energy storage system performs output power adjustment under over-limit conditions; otherwise, the energy storage system performs output power adjustment under non-over-limit conditions. The method for adjusting the output power of the energy storage system includes: determining an adjustment step size based on the maximum output power of the energy storage system; and gradually adjusting the output power according to the adjustment step size and the output power of the energy storage system at the previous moment.

7. The method according to claim 6, characterized in that, The method for regulating the output power of the energy storage system further includes: The initial value of the adjustment amount of the energy storage system is calculated based on the overload difference sample set.

8. The method according to claim 7, characterized in that, The method for calculating the initial value of the adjustment amount includes: The maximum and minimum values ​​in the overload difference sample set are selected; The initial value of the adjustment amount is obtained by dividing the maximum value by the minimum value.

9. The method according to claim 7, characterized in that, The method for determining the adjustment step size includes: The adjustment step size is obtained by dividing the interval between the initial value of the adjustment amount and the maximum value of the adjustment amount into equal parts.

10. A microgrid control device, characterized in that, include: The power prediction module is used to obtain the real-time power of the main transformer node, predict the power of the main transformer node based on the trend of the real-time power change within a preset time period, and determine the maximum output power of the energy storage system. The power adjustment module is used to determine the current output power of the energy storage system based on the power prediction result of the main transformer node and the maximum output power of the energy storage system, combined with the output power of the energy storage system at the previous moment, and control the output power of the energy storage system to follow the maximum output power according to the set adjustment amount. The power prediction module includes: An overload boundary threshold calculation unit is used to calculate the overload boundary threshold of the main transformer according to its specifications. The overload difference sample set construction unit is used to calculate the overload difference sample of the main transformer within the preset time period based on the overload boundary threshold and the real-time power within the preset time period, and to construct the overload difference sample set. The first power limit calculation unit is used to calculate a first power limit based on the trend of the values ​​in the overload difference sample set; wherein the first power limit is the maximum output power of the main transformer node.

11. A microgrid, characterized in that, include: A main transformer and an energy storage system, wherein the main transformer is used to convert the energy storage system and other systems in the microgrid, and the energy storage system performs the microgrid control method as described in any one of claims 1-9.

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